Hebrews 5:11
On this point I have a great deal to say, which it is hard to make intelligible to you. For you have grown dull of hearing.
2 Peter 3:16
speaking of this as he has done in all his letters ??letters containing some knotty points, which ignorant and unsteady souls twist (as they do the rest of the scriptures) to their own destruction.
Matthew 13:15
For the heart of this people is obtuse, their ears are heavy of hearing, their eyes they have closed, lest they see with their eyes and hear with their ears, lest they understand with their heart and turn again, and I cure them.
Mark 8:17-18
He noted this and said to them, "Why do you argue you have no bread? Do you not see, do you not understand, even yet? Are you still dull of heart?
Mark 8:21
"Do you not understand now?" he said.
Luke 24:25
He said to them, "O foolish men, with hearts so slow to believe, after all the prophets have declared!
John 6:6
(He said this to test Philip, for he knew what he was going to do himself.)
John 16:12
I have still much to say to you, but you cannot bear it just now.
Acts 28:27
For the heart at this people is obtuse, their ears are heavy at hearing, their eyes they have closed, lest they see with their eyes and hear with their ears, lest they understand with their heart and turn again, and I cure them.